Photofabrication, which is now the mainstream of microfabrication techniques, is a generic term describing the technology used for manufacturing a wide variety of precision components, such as semiconductor packages. The manufacturing is carried out by coating a photosensitive resin composition to the surface of a processing target to form a coating, patterning this coating using photolithographic techniques, and then conducting electroforming based mainly on chemical etching or electrolytic etching, and/or electroplating, using the patterned coating as a mask.
In recent years, high density packaging technologies have progressed in semiconductor packages along with downsizing electronics devices, and the increase in package density has been developed on the basis of mounting multi-pin thin film in packages, miniaturizing of package size, two-dimensional packaging technologies in flip-tip systems or three-dimensional packaging technologies. In these types of high density packaging techniques, connection terminals, including protruding electrodes (mounting terminals) known as bumps that protrude above the package or metal posts that extend from peripheral terminals on the wafer and connect rewiring with the mounting terminals, are disposed on the surface of the substrate with high precision.
The materials used in the photofabrication described above are typically photoresists for a thick film. The photoresists for a thick film are employed for forming thick photoresist layers and are used, for example, to form bumps or metal posts in plating processes. Bumps or metal posts can be formed, for example, by producing a thick resist layer of about 20 μm in thickness on a support, exposing the resist layer through a predetermined mask pattern, developing the layer to obtain a resist pattern in which the portions for forming the bumps or metal posts are selectively removed (stripped), embedding a conductor such as copper into the stripped portions (resist-free portions) using plating, and then removing the surrounding residual resist pattern.
In regards to the photoresists for a thick film, a positive-type photosensitive resin composition, employed for forming bumps or wirings, is disclosed that includes a quinone diazide group-containing compound (see Japanese Unexamined Patent Application Publication No. 2002-258479).
On the other hand, chemically amplified photoresists including an acid generator have been known as a photosensitive resin composition that is more sensitive than conventional positive-type photosensitive resin compositions that include a quinone diazide group-containing compound. The chemically amplified photoresists are characterized in that an acid is generated from the acid generator upon irradiation with radiation (exposure) and diffusion of the acid is promoted through heat treatment after the exposure, to cause an acid catalytic reaction with a base resin in the resin composition resulting in a change to the alkali-solubility of the base resin. Among the chemically amplified photoresists, chemically amplified photoresist compositions for plating are disclosed as positive type photoresists which transform from alkali insoluble to alkali soluble (for example, see Japanese Unexamined Patent Application Publication Nos. 2001-281862 and 2001-281863).    Patent Document 1: Japanese Unexamined Patent Application Publication, First Publication No. 2002-258479    Patent Document 2: Japanese Unexamined Patent Application Publication, First Publication No. 2001-281862    Patent Document 3: Japanese Unexamined Patent Application Publication, First Publication No. 2001-281863    Patent Document 4: Japanese Unexamined Patent Application Publication, First Publication No. 2006-258479